Synopsis
In the opening sequence, Dexter fends off his arch-rivalMandark from stealing his latest invention, the Neurotomic Protocore. Sometime later, Dexter is attacked in his lab by killer robots seeking "the one who saves the future". Dexter, after defeating the robots and utilizing his extensive but egotism-warped brainpower, assumes "the one who saves the future" must be him. So, he goes into the future with the help of his time machine, and meets three versions of himself:

-A nerdy paper pusher version of himself who, in the near future toils under Mandark in a corporation straight out of the movie Brazil , and has yet to save the future.
-A senile old man version of himself who reigns over an enlightend, peaceful technocracy in the far future, but can barely remember what he's doing, yet alone how he saved the future. (Mandark is currently a brain in a jar, doing time in a museum devoted to Dexter)
-A macho, balding (the far-future Dexter wears a wig), Sons of Ether-meets-Arnold Schwarzenegger version of himself who combats Mandark, currently an evil overlord who stole the aforementioned Neurotomic Protocore and used it to suck the brainpower out of everyone on earth (Mandark also physically resembles one of the hideouslyobese Barons from Dune).

The four Dexters team up to stop Mandark, who has seen this coming and brought each of the other three time periods' respective Mandarks along. After a big knock-down drag-out fight, Dexter discovers much to his chagrin that it was Dee-Dee who saved the future when she teleports into the middle of the fracas, walks up to Mandark's evil machine and simply turns it off! He then goes on to build the machines that attacked him earlier in order to get Dee-Dee! But most of the irony of the situation is lost to Dexter when he gets home; he just shrugs it off and goes back to his work.